1. Field of the Invention
The present invention relates to semiconductor devices including semiconductor sensor chips for detecting variations of pressure such as variations of sound pressure applied thereto.
This application claims priority on seven Japanese Patent Applications whose numbers are 2005-376396, 2005-354458, 2006-48351, 2006-21164, 2005-354459, 2006-303717, and 2006-303837, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, semiconductor devices such as silicon-capacitor microphones and pressure sensors, in which semiconductor chips having thin-film diaphragms for detecting variations of sound pressure are mounted on the surfaces of the printed boards, have been developed. For example, Japanese Patent Application Publication No. 2004-537182 teaches an example of a silicon-capacitor microphone. This kind of semiconductor senor chip detects variations of pressure such as variations of sound pressure due to vibration of a diaphragm, wherein detection sensitivity can be increased by increasing the size of the diaphragm. Hence, it is preferable that the semiconductor sensor chip be increased in size in order to increase the detection sensitivity.
The aforementioned semiconductor devices have been installed in handy-type electronic devices such as portable telephones (or cellular phones); hence, it is strongly demanded to downsize them. Japanese Unexamined Patent Application Publication No. 2000-349305 teaches another example of a semiconductor device realizing downsizing, in which outer leads establishing electric connection with a semiconductor sensor chip are arranged only in one long side of a package.
When the aforementioned semiconductor device is mounted on a printed-circuit board of an electronic device, outer leads arranged only in one long side of a package are fixed to the connection terminals of the printed-circuit board by way of soldering. This makes the installation of the semiconductor device mounted on the printed-circuit board unstable.
It may be possible to combine the technical features of the aforementioned semiconductor devices; however, when the semiconductor device mounted on the printed-circuit board vibrates, the diaphragm may not accurately detect pressure variations due to vibration.
In addition, the conventionally-known semiconductor devices such as the pressure sensors and silicon-capacitor microphones are designed such that semiconductor sensor chips having rectangular shapes and recesses are mounted on printed boards, wherein the thinned portions of the recesses are used as diaphragms (or moving electrodes) having bridge-resistance circuits, wherein the bridge-resistance circuits detect the displacement (or deformation) of the diaphragms caused by sound pressure as variations of electric resistance, based on which variations of sound pressure are detected.
In the aforementioned semiconductor devices, cover members are arranged above the surfaces of the printed boards so as to form internal spaces embracing semiconductor sensor chips therein. The cover members have opening holes establishing communications between the internal spaces and the external space, whereby it is possible to transmit variations of sound pressure, which occur in the external space, toward the semiconductor sensor chips in the internal spaces via the opening holes. Conductive layers are formed on the interior surfaces of the cover members so as to block electromagnetic noise, which is transmitted into the internal spaces via the opening holes, from being transmitted toward the semiconductor sensor chips by way of electromagnetic shields. This reliably avoids the occurrence of error vibrations on the diaphragms due to electromagnetic noise reaching the semiconductor sensor chips; thus, it is possible to accurately detect variations of sound pressure. This technology is disclosed in Japanese Patent Application Publication No. 2004-537182 and U.S. Pat. No. 6,781,231, for example.
In the above, it is necessary to provide a special means establishing electrical connection between the conductive layer of the cover member and the printed-circuit board when the aforementioned semiconductor device is mounted on the printed-circuit board of a portable telephone and the like.
In order to form an electromagnetic shield in the aforementioned semiconductor device, the cover member should be arranged such that the conductive layer of the cover member substantially matches in position with the connection terminals formed on the upper surface of the printed board. In other words, fine precision is required to prevent electrical discontinuity between the conductive layer of the cover member and the connection terminals of the printed board; hence, it is troublesome for the human operator (or worker) to precisely arrange the cover member in connection with the printed board.